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/*
*
* hostfile.c
*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* Created: Thu Jun 29 07:10:56 1995 ylo
*
* Functions for manipulating the known hosts files.
*
*/
#include "includes.h"
RCSID("$OpenBSD: hostfile.c,v 1.16 2000/04/14 10:30:31 markus Exp $");
#include "packet.h"
#include "match.h"
#include "ssh.h"
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include "key.h"
#include "hostfile.h"
/*
* Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the
* pointer over the key. Skips any whitespace at the beginning and at end.
*/
int
hostfile_read_key(char **cpp, unsigned int *bitsp, Key *ret)
{
unsigned int bits;
char *cp;
/* Skip leading whitespace. */
for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
;
/* Get number of bits. */
if (*cp < '0' || *cp > '9')
return 0; /* Bad bit count... */
for (bits = 0; *cp >= '0' && *cp <= '9'; cp++)
bits = 10 * bits + *cp - '0';
if (!key_read(ret, bits, &cp))
return 0;
/* Skip trailing whitespace. */
for (; *cp == ' ' || *cp == '\t'; cp++)
;
/* Return results. */
*cpp = cp;
*bitsp = bits;
return 1;
}
int
auth_rsa_read_key(char **cpp, unsigned int *bitsp, BIGNUM * e, BIGNUM * n)
{
Key *k = key_new(KEY_RSA);
int ret = hostfile_read_key(cpp, bitsp, k);
BN_copy(e, k->rsa->e);
BN_copy(n, k->rsa->n);
key_free(k);
return ret;
}
int
hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum)
{
if (key == NULL || key->type != KEY_RSA || key->rsa == NULL)
return 1;
if (bits != BN_num_bits(key->rsa->n)) {
error("Warning: %s, line %d: keysize mismatch for host %s: "
"actual %d vs. announced %d.",
filename, linenum, host, BN_num_bits(key->rsa->n), bits);
error("Warning: replace %d with %d in %s, line %d.",
bits, BN_num_bits(key->rsa->n), filename, linenum);
}
return 1;
}
/*
* Checks whether the given host (which must be in all lowercase) is already
* in the list of our known hosts. Returns HOST_OK if the host is known and
* has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED
* if the host is known but used to have a different host key.
*/
HostStatus
check_host_in_hostfile(const char *filename, const char *host, Key *key, Key *found)
{
FILE *f;
char line[8192];
int linenum = 0;
unsigned int kbits, hostlen;
char *cp, *cp2;
HostStatus end_return;
if (key == NULL)
fatal("no key to look up");
/* Open the file containing the list of known hosts. */
f = fopen(filename, "r");
if (!f)
return HOST_NEW;
/* Cache the length of the host name. */
hostlen = strlen(host);
/*
* Return value when the loop terminates. This is set to
* HOST_CHANGED if we have seen a different key for the host and have
* not found the proper one.
*/
end_return = HOST_NEW;
/* Go trough the file. */
while (fgets(line, sizeof(line), f)) {
cp = line;
linenum++;
/* Skip any leading whitespace, comments and empty lines. */
for (; *cp == ' ' || *cp == '\t'; cp++)
;
if (!*cp || *cp == '#' || *cp == '\n')
continue;
/* Find the end of the host name portion. */
for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++)
;
/* Check if the host name matches. */
if (!match_hostname(host, cp, (unsigned int) (cp2 - cp)))
continue;
/* Got a match. Skip host name. */
cp = cp2;
/*
* Extract the key from the line. This will skip any leading
* whitespace. Ignore badly formatted lines.
*/
if (!hostfile_read_key(&cp, &kbits, found))
continue;
if (!hostfile_check_key(kbits, found, host, filename, linenum))
continue;
/* Check if the current key is the same as the given key. */
if (key_equal(key, found)) {
/* Ok, they match. */
fclose(f);
return HOST_OK;
}
/*
* They do not match. We will continue to go through the
* file; however, we note that we will not return that it is
* new.
*/
end_return = HOST_CHANGED;
}
/* Clear variables and close the file. */
fclose(f);
/*
* Return either HOST_NEW or HOST_CHANGED, depending on whether we
* saw a different key for the host.
*/
return end_return;
}
/*
* Appends an entry to the host file. Returns false if the entry could not
* be appended.
*/
int
add_host_to_hostfile(const char *filename, const char *host, Key *key)
{
FILE *f;
int success = 0;
if (key == NULL)
return 1;
/* Open the file for appending. */
f = fopen(filename, "a");
if (!f)
return 0;
fprintf(f, "%s ", host);
if (key_write(key, f)) {
fprintf(f, "\n");
success = 1;
} else {
error("add_host_to_hostfile: saving key failed");
}
/* Close the file. */
fclose(f);
return success;
}
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